说到文件上传我们要做到：

1.引入两个包：commons-fileupload-1.2.1.jar和commons-io-1.3.2.jar

2.将form改为上传文件模式：enctype="multipart/form-data"

3.开始编写相关代码

这里会用到几个关键的类：磁盘文件工厂DiskFileItemFactory ； 创建servlet文件上传类：ServletFileUpload

还有几个重要的方法：DiskFileItemFactory类用于将以临时文件形式保存在磁盘上的存放目录的方法setRepository；

ServletFileUpload类得到表单中所有的数据，得到form表单中所有的元素方法：parseRequest

下面看具体代码：

说明以这种方式上传文件是保存在服务器端的！

import java.io.File;

import java.io.IOException;

import java.io.PrintWriter;

import java.util.ArrayList;

import java.util.List;

import java.util.UUID;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import org.apache.commons.fileupload.FileItem;

import org.apache.commons.fileupload.FileUploadException;

import org.apache.commons.fileupload.disk.DiskFileItemFactory;

import org.apache.commons.fileupload.servlet.ServletFileUpload;

import org.apache.commons.io.FileUtils;

public class UploadServlet extends HttpServlet {

/**

* Constructor of the object.

*/

public UploadServlet() {

super();

}

/**

* Destruction of the servlet.

*/

public void destroy() {

super.destroy(); // Just puts "destroy" string in log

// Put your code here

}

/**

* The doGet method of the servlet.

*

* This method is called when a form has its tag value method equals to get.

*

* @param request the request send by the client to the server

* @param response the response send by the server to the client

* @throws ServletException if an error occurred

* @throws IOException if an error occurred

*/

public void doGet(HttpServletRequest request, HttpServletResponse response)

throws ServletException, IOException {

this.doPost(request, response);

}

/**

* The doPost method of the servlet.

*

* This method is called when a form has its tag value method equals to post.

*

* @param request the request send by the client to the server

* @param response the response send by the server to the client

* @throws ServletException if an error occurred

* @throws IOException if an error occurred

*/

public void doPost(HttpServletRequest request, HttpServletResponse response)

throws ServletException, IOException {

response.setContentType("text/html");

PrintWriter out = response.getWriter();

DiskFileItemFactory sf= new DiskFileItemFactory();//实例化磁盘被文件列表工厂

String path = request.getRealPath("/upload");//得到上传文件的存放目录

sf.setRepository(new File(path));//设置文件存放目录

sf.setSizeThreshold(1024*1024);//设置文件上传小于1M放在内存中

String rename = "";//文件新生成的文件名

String fileName = "";//文件原名称

String name = "";//普通field字段

//从工厂得到servletupload文件上传类

ServletFileUpload sfu = new ServletFileUpload(sf);

try {

List lst = sfu.parseRequest(request);//得到request中所有的元素

for (FileItem fileItem : lst) {

if(fileItem.isFormField()){

if("name".equals(fileItem.getFieldName())){

name = fileItem.getString("UTF-8");

}

}else{

//获得文件名称

fileName = fileItem.getName();

fileName = fileName.substring(fileName.lastIndexOf("\\")+1);

String houzhui = fileName.substring(fileName.lastIndexOf("."));

rename = UUID.randomUUID()+houzhui;

fileItem.write(new File(path, rename));

}

}

} catch (Exception e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

System.out.println("普通字段"+name);

System.out.println("文件名称"+fileName);

System.out.println("修改后生成的文件名称"+rename);

response.sendRedirect("ok.jsp");

out.flush();

out.close();

}

/**

* Initialization of the servlet.

*

* @throws ServletException if an error occurs

*/

public void init() throws ServletException {

// Put your code here

}

}

index.jsp页面：

文件测试界面

ok.jsp页面：

上传文件成功!

实现效果就不截图了，有需要自己那过去用！

以上这篇java文件上传Demo(必看篇)就是小编分享给大家的全部内容了，希望能给大家一个参考，也希望大家多多支持我们。

时间： 2017-05-09